1. Field of the Invention
The present invention relates to a control device of an engine that is installed on a vehicle etc. and, in particular, to a control device of a direct injection engine, the control device that is provided with an injector directly injecting fuel into a cylinder (a combustion chamber) and performs idle stop to stop the engine temporarily when the engine and a vehicle equipped with the engine are in a state in which the engine and the vehicle satisfy a predetermined condition.
2. Description of the Related Art
In recent years, from the viewpoint of environmental conservation, vehicles (automobiles) have been expected to achieve a reduction of combustion waste gas (exhaust gas) which turns into greenhouse gas and a reduction of carbon monoxide (CO), hydrocarbon (HC), nitrogen oxides (NOx), etc. which are contained in the combustion waste gas (exhaust gas) (these reductions are referred to as “an improvement in exhaust performance) and a reduction of fuel consumption (an improvement in fuel efficiency), and a direct injection engine that makes an injector directly perform fuel injection into a combustion chamber of each cylinder has been developed to achieve primarily improvements in exhaust performance and fuel efficiency and an improvement in engine output.
Moreover, a vehicle with an idle stop function of performing idle stop to stop an engine temporarily when the engine and a vehicle equipped with the engine are in a state in which the engine and the vehicle satisfy a predetermined condition (for example, a state in which the vehicle stops at a red light) and then restarting the engine by driving a starter upon a restart request to achieve further improvements in fuel efficiency and exhaust performance has also been put to practical use and come into wide use.
Various techniques related to idle stop (engine stop) and restarting in a vehicle equipped with a direct injection engine have been proposed. For example, JP-A-2010-236546 proposes a technique of determining whether or not a stop position of a piston of a certain cylinder is a stop position in which compression injection combustion can be performed and starting fuel injection when the piston stop position in the cylinder is a specific position in which compression injection combustion can be performed.
Moreover, for example, JP-A-2007-23815 proposes a technique of making a compression stroke cylinder inject fuel and ignite the fuel when a restart request is made before an engine (rotation) is stopped after an idle stop condition is satisfied and the engine rotation speed at that time is higher than a predetermined value and making the compression stroke cylinder and an expansion stroke cylinder inject fuel and ignite the fuel when the engine rotation speed is lower than the predetermined value.
As described above, in recent years, in a direct injection engine that is installed on a vehicle with an idle stop function, various restarting techniques to achieve primarily improvements in fuel efficiency and exhaust performance have been proposed. To achieve further improvements in fuel efficiency and exhaust performance, the number of times an idle stop (engine stop) condition is satisfied is increasing, and a restarting technique used when a restart request is made based on, for example, the driver's intention before the engine (rotation) is stopped becomes more important.
A restart request before the engine (rotation) is stopped after an idle stop (engine stop) condition is satisfied is determined by the driver's intention. However, various piston positions at the time of issuance of the restart request and combustion at the time of extremely low rotation result in unstable combustion and eventually an increase in the amount of emission of soot caused by misfire and poor exhaust performance if an appropriate fuel injection (injection start timing and injection time=injection quantity) is not performed.